That is because grub2 1.99 did own /boot/grub/grub.cfg, so upgrading to grub2 2.00 would result in that file being moved to its .pacsave entry.
To avoid this, which would break systems, I'll restore the old configuration, so that the configuration on disk and the bootloader in the MBR should match.
Any other choice (automatically run grub-mkconfig, or automatically run grub-install) is conceptually wrong and could lead to unwanted results or broken systems.
Removed a routine which only mattered to 2.6 kernels, which we stopped shipping like one year ago.
Stopped running update-grub automatically, or it will mean that a user might have an older GRUB installed in its MBR reading a configuration file targeted for a newer GRUB, thus failing in some funny ways.
The old script only did this in the post_upgrade() hook if there was a
/boot/grub/grub.cfg file with non-zero size, but as we already tell pacman
to backup that file, we can safely regenerate it anyway.
